1. Field
The following description relates to passive optical network technology, and more particularly, to a method and device for selecting a wavelength of an optical network unit in a passive optical network.
2. Description of the Related Art
A passive optical network (PON) is a subscriber network that connects a central office and a subscriber with a point-to-multipoint topology and is cost effective compared to a structure having a point-to-point topology since required central office systems and optical cables can be reduced.
Currently, as a high-speed optical subscriber network, a time division multiplexing passive optical network (TDM-PON), for example, an Ethernet PON (EPON) and a Gigabit-capable PON (GPON), is being widespread through the world. Particularly, the GPON is deployed in many areas of the world. In 2010, the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) completed recommendation of G.987 XG-PON standard (10G-GPON). Recently, early commercial products based on the G.987 are being released.
Recently, as a wavelength division multiplexing optical subscriber network for providing voice, data, and a broadcasting convergence service, research and development on a wavelength division multiplexing passive optical network (WDM-PON) are being active. In the WDM-PON, communication between a central base station and a subscriber is performed using a respective wavelength assigned to each subscriber. Since a dedicated wavelength per subscriber is used, security is excellent and a mass communication service is possible. Moreover, it is possible to apply different transmission technology per subscriber or per service.
Furthermore, the Full Service Access Network (FSAN) Group, which is a standardization group consisting of major communication operators and equipment manufacturers associated with optical subscriber network technology, adopted a time and wavelength division multiplexing passive optical network (TWDM-PON) that is a hybrid type passive optical network using time division multiplexing and wavelength division multiplexing at the same time, as major technology of a next-generation passive optical network (NG-PON2). Therefore, the ITU-T is discussing recommendation for G.ngpon2.x standards.
In order to register an optical network unit/optical network terminal (ONU/ONT, hereinafter referred to as an ‘ONU’ or a ‘terminal’) in this hybrid type passive optical network and perform a communication, it is necessary for the terminal to assign a wavelength to be used initially. Methods of assigning an initial available wavelength for the terminal include, a method in which a terminal is firstly connected to a master optical line terminal (OLT) and the master OLT assigns a wavelength to be used in the terminal and informs the terminal of the wavelength, and a method in which an arbitrary wavelength is selected as an initial wavelength and a firstly connected OLT informs the terminal of the wavelength to be used.
However, these methods require the master OLT to know conditions of all other OLTs in advance or each OLT to know conditions of all other OLTs in advance. In addition, it is difficult to use in a network in which systems supporting different protocols are mixed, for example, the EPON and the GPON. Further, since contents are not defined in the existing OLT, it is difficult to implement and manage.